The equilibrium configurations of an array of straight parallel disloc
ations and planar defects bounded by dislocations in a solid are consi
dered. On the basis of dimensional arguments and using Euler's theorem
for homogeneous functions, it can be shown that the total internal su
rface energy of the planar defects is constant for all possible unrest
rained equilibrium configurations of the array and is equal to the sum
of all pre-logarithmic interaction energy factors.